Fixing the batch photo delete test.

I broke the test with a different commit, and this fixes it.

Author: stmott

spec/fixtures/listings/photos/batch_delete.json

@@ -0,0 +1,10 @@
+{
+    "D": {
+        "Results": [
+            {
+                "Id": "20060725225010201442000000,20060918191319441822000000"
+            }
+        ],
+        "Success": true
+    }
+}

spec/unit/spark_api/models/listing_spec.rb

@@ -358,8 +358,8 @@
           l = Listing.find(list_id, :_expand => "Photos")
           photo_id1 = l.photos[0].Id
           photo_id2 = l.photos[1].Id
-          stub_api_delete("/listings/#{list_id}/photos/#{photo_id1},#{photo_id2}", 'success.json')
-          l.delete_photos(photo_id1 + "," + photo_id2).should be(true)
+          stub_api_delete("/listings/#{list_id}/photos/#{photo_id1},#{photo_id2}", 'listings/photos/index.json')
+          l.delete_photos(photo_id1 + "," + photo_id2).should_not be_empty
         end
       end
     end